Next you call appropriate function and get either result of parsing
identical to that of Cassava or error message. The error message is
well-typed so you can examine it in Haskell code easily. Conversion error
are considered parsing errors by the cassava-megaparsec package and are
reported via custom error message component Cec supported by Megaparsec 5.
Since Cassava’s conversion errors are plain strings, we have no choice but
to represent them as strings too: